Gift to certain users

You don't outline why you need to do this, or how many, etc., which tends to limit suggestions outright. Talk about your scheme.

How many is 'certain' users? Who are they?

If small numbers (tens), consider redeem codes or gifting, if larger (hundreds/thousands) consider making your app free/no-cost for a limited time, etc.

"offer licenses to users"

It is unclear what you mean by 'license'.

There are promo codes (up to 100?) for a paid app and also for IAPs.

You can also use TestFlight.

Yes, sorry for the lack of precision.

We, I would like to allow friends (less than 10 people) to access the software.

The problem is that I can't use TestFlight because my application only works under macos.

Another possibility. Give the apk file to install directly on the machine without going through Apple Store?

>my application only works under macos. ~ would like to allow friends (less than 10 people) to access the software.

Suggest you utilize redeem/promo codes in that case. Just remember that they won't be able to leave reviews.

Good luck.